It’s called "frequent locations," and it's stored deep in a maze of privacy settings. It tracks time, dates and how long you stay somewhere. It even knows where you live and work, based on your time and trips there.

“That’s pretty scary -- I would never know a phone would have that much access,” iPhone user Allie Salgado said.

Patrick J. Brosnan is a security expert and a retired NYPD detective. He likened the feature to a Pandora’s Box for law enforcement.

“It has become easier for people to cheat. It’s easier to find out if people are cheating,” he said.

HERE’S HOW TO TURN ‘FREQUENT LOCATIONS’ OFF:

APPLE DEVICES
1. Click "Settings"
2. Go to "Privacy"
3. Select "Location Services"
4. Scroll down to "System Services"
5. Choose "Frequent Locations" to see the logged record of where you've been -- de-select this to turn the feature off

ANDROID DEVICES
Open the App Drawer and go to Settings.
Scroll down and tap Location.
Scroll down and tap Google Location Settings.
Tap Location Reporting and Location History, and switch the slider to off for each one.
To delete your phone's location cache, tap "Delete Location History" at the bottom of the screen under Location History.
Repeat this process for each Google Account you have on your Android device.